To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post LTE system’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like.
In the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Device to Device (D2D) communication is being studied in communication standard groups to enable data communication services between the UEs. During the D2D communication a transmitting D2D UE can transmit data packets to a group of D2D UEs or broadcast data packets to all the D2D UEs. D2D communication between the transmitter and receiver(s) is connectionless in nature i.e. there is no connection setup between the transmitter and receiver before the transmitter starts transmitting the data packets. During the transmission, the transmitter includes the source ID and the destination ID in the data packets. The source ID is set to the UE ID of the transmitter. The destination ID is the broadcast ID or group ID of intended recipient of the transmitted packet.
A D2D UE (i.e. Remote UE) can communicate with network via another D2D UE (i.e. UE-to-Network Relay). The D2D direct discovery procedure is used to discover UE-to-Network relay. The UE capable of supporting the UE-to-Network relay functionality and in coverage of network periodically broadcasts User Equipment (UE)-to-Network Relay indication (i.e. discovery message indicating itself as the UE-to-Network relay). The discovery message is transmitted on D2D discovery channel. The remote UE interested in searching for UE-to-Network Relay monitors D2D discovery channel for receiving the UE-to-Network relay indication (i.e. discovery message indicating itself as the UE-to-Network relay) transmitted by the UE-to-Network Relay in its proximity. Although, there may not be any Remote UEs in vicinity, to the UE-to-Network relay, and also the Remote UEs if in the vicinity may not be in need of UE-to-Network Relay to communicate with the network.
As a result, the UE capable of supporting the UE-to-Network relay broadcasting the discovery message periodically may unnecessarily leads to the wastage of resources and increased power consumption in the UE.
Thus, there exists a need of robust and efficient mechanism for triggering the transmission of UE-to-Network relay indication (i.e. discovery message indicating itself as the UE-to-Network relay) by the UE, capable of supporting UE-to-Network relay functionality.